This proposal is a continuation of an ongoing epidemiologic study of HIV-1 infection amount intravenous drug users. This study proposes to: 1) Estimate the incidence of antibodies to HIV-1 among a cohort of IVDUs; 2) Conduct a case-control study of incident seropositive IVDU cases and seronegative controls; 3) Estimate mortality rates for seroprevalent, seroincident and seronegative IVDUs; and 4) Conduct survival analysis to estimate relative survival from time of seroconversion to death or the common closing of he study and to determine prognostic factors that related to survival and death. The cohort of 700 IVDUs that is being followed in the initial grant will form the primary study sample for this continuation. In order to address Aims 1, 3 and 4, this cohort of 700 IVDUs who have been tested for sero-status while in drug treatment programs will be followed at 6 month intervals for 2.5 years. When combined with data from the original grant, 3.5 to 4.5 years of follow-up data will be available for analysis. In addition, IVDUs from an AIDS risk reduction program will be pooled with the cohort of 700 to accrue sufficient cases to carry out the case-control study-AIM 2. There are four phases to this project. In phase 1, the original cohort of IVDUs who tested negative at baseline for HIV-1 AB will be rescreened at 6 month intervals for seroconversion to determine the proportion who seroconvert (become HIV AB+). In phase 2, individuals who seroconvert (seroincident cases) will be pooled with seroincident cases from the risk reduction program to accrue cases for the case-control study. Four controls (seronegative subjects) per case will be randomly selected from the seronegative pool. Phase 3 will use follow-up data to estimate morality rates among subgroups in the original cohort. Phase 4 will perform survival analysis, estimate relative survival and determine prognostic factors for survival.